Hello,
Firstly, what version of Kentico
CMS do you use? Do you have applied any hotfix?
I tested that in version 5.5.23 and 5.0.0 and it works fine with default value set to false.
Could you please provide us with detailed description of your custom table bit field?
Also please let us know exact error message. Thanks in advance. Some screenshots would be greatly appreciated.
Furthermore, do you have any related customizations?
Best regards
Ondrej Vasil